Device for the Monitored Filling of Containers with Tablets

ABSTRACT

A device for the monitored filling of containers with tablets which includes a feed device for feeding tablets to a free-fall section and a capacitive sensor for checking each falling tablet in the free-fell section. In addition, the device includes a separating device for separating the bad tablets from the good tablets, the separating device being located below or underneath the sensor in the free-fall section. A control unit is included which is connected to the separating device and which actuates the separating device on the basis of the values supplied by the capacitive sensor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority based on European patent applications EP 07 017 103.8, filed Aug. 31, 2007, and EP 08 014 637.6, filed on Aug. 18, 2008.

FIELD OF THE INVENTION

The invention pertains to a device for the monitored filling of containers with tablets.

Strict quality criteria must be met during the filling of containers with pharmaceutical products. Various known types of sensors are used for monitoring the process of filling drug containers such as cans or small bottles with pharmaceutical products. These sensors are used to count the number of tablets as they are falling into the container and thus to guarantee that the container has been filled correctly. Light barriers are used most frequently for this, but they can become dirty. The use of electrostatic sensors has also been considered.

A filling device with a capacitive measuring sensor is known from U.S. Pat. No. 4,461,363. The sensor checks the weight of the falling tablets. Nevertheless, any container which contains a defective tablet must be sorted out, which leads to a large number of unnecessarily rejected tablets.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a device for the monitored filling of containers with tablets which operates very reliably, which makes it possible for the tablets to be checked quantitatively very quickly during the filling process, and which does not unnecessarily remove good tablets during the filling process A corresponding method for the monitored filling of containers with tablets is also provided as a desired object of the invention.

According to an aspect of the invention, the device for the monitored filling of containers with tablets comprises a device for feeding tablets to a free-fall section and a capacitive sensor for checking each of the falling tablets in the free-fall section. The device for the monitored filling of containers also comprises a separating device for separating the bad tablets from the good tablets, the separating device being located below or underneath the sensor in the free-fall section. The device of the present invention also includes a control unit, which is connected to the sensor and to the separating device and which actuates the separating device on the basis of the values supplied by the sensor.

It is thus possible to check the tablets quantitatively during the filling process itself. By ejecting the bad tablets even before they reach the container to be filled, the number of good tablets which are sorted out is reduced to zero.

The sensor preferably includes a voltage generator for a generating a high-frequency alternating electrical field; two opposing, vertically oriented capacitor plates, which are given opposite, rapidly reversing charges by the voltage generator; and an ammeter.

The alternating electrical field preferably has a frequency in the range between approximately 500 kilohertz (kHz) and approximately 10 megahertz (MHz), and especially a frequency of approximately 1 megahertz (MHz).

With this arrangement, the sensor is able to detect more than approximately 1,000 tablets per minute. The sensor is preferably also able to record the data for a tablet within a time window of less than approximately 100 milliseconds (ms), more preferably of less than approximately 50 Milliseconds (ms), and even more preferably of less than approximately 10 (ms), which represents a prerequisite for the exact and rapid actuation of the separating device.

In one embodiment, the capacitor plates comprise a height of approximately 5 millimeters (mm) to approximately 20 millimeters (mm), and preferably of approximately 10 millimeters (mm). The distance between the capacitor plates is in the range of approximately 5 mm to approximately 30 mm but is at least 10% larger than the width of a tablet.

In another embodiment, the device of the present invention may also comprise a camera, which is installed above the sensor and is connected to the control unit. In this case, the control unit is adapted to use the values supplied by the sensor and the information concerning a specific tablet supplied by the camera as a common basis for the actuation of the separating device. Thus, by way of an example only and not limiting in any manner, not only tablets which have the wrong weight but also tablets with the correct weight but the wrong color may be sorted out.

In an additional preferred embodiment, the separating device is designed as an air blast unit, which directs a jet of air sideways against the selected falling tablet. This guarantees that the bad tablets are sorted out accurately without interfering with the operation of the filling device even when the filling operation is proceeding rapidly.

The inventive method for the monitored filling of containers with tablets comprises the following steps:

-   -   feeding tablets to a free-fall section;     -   checking each falling tablet in the free-fall section by means         of a capacitive sensor; and     -   separating, in a controlled manner, the bad tablets from the         good tablets in the free-fall section underneath or below the         capacitive sensor on the basis of the values supplied by the         capacitive sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional details, features, and advantages of the present invention can be derived from the following description and drawings in which:

FIG. 1 is a schematic view of an exemplary embodiment of the device for the monitored filling of containers with tablets; and

FIG. 2 is a schematic diagram of the sensor used in the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

FIG. 1 is a schematic view of an exemplary embodiment of the present invention for the monitored filling of containers with tablets. The device comprises a feed device 2 for tablets 4, such devices usually being designed as vibratory conveyors. The tablets have already been spaced apart from each other by feed device 2. From feed device 2, tablets 4 proceed to a free-fall section 6, through which they fall into containers 14 which may be by way of example, cans or bottles. Containers 14 are transported by a conveyor device 20. A sensor 12 for recording quantitative properties, especially the weights of tablets 4, is located in free-fall section 6. In the illustrated embodiment, sensor 12 is located in the upper area of free-fall section 6.

As will be described in greater detail below, sensor 12 transmits the measured values to a control unit 7, which is itself adapted to transmit immediately (i.e., preferably within approximately 10 ms), a control command to a separating device 8 on the basis of the values transmitted by sensor 12. Separating device 8 is responsible for separating tablets 4, specifically bad tablets from the good tablets. In the present example, as tablets 4 are sorted out actively, bad tablets maybe removed but it is also conceivable that each good tablet could be conducted actively into container 14 by separating device 8. As shown in FIG. 1, separating device 8 is illustrated preferably as an air blast device, which accurately aims a jet of air sideways at specific tablet 4. An air blast device of this type offers the advantage over mechanical devices in that the reaction time is much shorter, which guarantees accuracy even in a filling device with a high throughput. Bad tablets land in a reject container 9 a.

To calculate the exact time at which separating device 8 is to be activated, control unit 7 preferably takes into account the size and the velocity of individual tablets 4 on the basis of previously recorded calibration values. Because of the high speed of sensor 12, of control unit 7, and of separating device 8, separating device 8 can be located below and underneath sensor 12.

In addition, a camera 11, for example a color camera, can be installed above feed device 2 and record information concerning individual tablets 4. This information can also be used by control unit 7 to actuate separating device 8. The image data may require a longer processing time than the sensor data. Thus both tablets 4 with the wrong weight (as determined by sensor 12) and tablets 4 with the wrong color (as determined by camera 11) can be rejected.

In coordination with the detection of tablets 4, a filling control system 9 can also be actuated by control unit 7 as soon as a certain number of good tablets 4 have arrived in container 14. As is shown in FIG. 1, it is preferable, after container 14 has been completely filled, for filling control system 9 to initiate the filling of next container 14 by the use of movable filling means 10. Movable filling means 10 mat include a feed channel, for example, which is pivoted into position, or a storage flap in the feed channel, which is temporarily closed and reopened. For this purpose, conveyor device 20 is also preferably moved further along in a stepwise manner, so that next container 14 is brought into the filling position.

FIG. 2 is a perspective diagram illustrating a design of sensor 12. Sensor 12 is designed as a capacitive measuring sensor and comprises two opposing, vertically oriented capacitor plates 15, 16, between which tablets 4 fall. Capacitor plates 15, 16 are given opposite, rapidly reversing charges by a voltage generator 13 for high-frequency AC voltage. The frequency is between approximately 500 kHz and approximately 10 MHz, and preferably approximately 1 MHz. The charge states of capacitor plates 15, 16 under application of opposite voltages are shown in two diagrams, 2 a and 2 b of FIG. 2. In FIG. 2 a, capacitor plate 15 is positively charged, and capacitor plate 16 is negatively charged. In FIG. 2 b, capacitor plate 16 is positively charged and capacitor plate 15 is negatively charged.

As a result of the reversing applied voltage U_(Generator)(t), very small polarization changes occur in tablet 4, winch in itself represents an insulator, in the alternating field. These very small polarization changes can be detected by an ammeter 18. The measured current I_(M)(t) is proportional to the number of charged particles in tablet 4. Excellent results are obtained even while tablet 4 are falling and during the corresponding extremely short time that each tablet 4 is located in the area of sensor 12. Accurate measurements are maintained even during the continuous acceleration of tablets 4 through sensor 12.

The details of the design of sensor 12 can vary widely, as long as the basic structure described in FIG. 2 is preserved. In a preferred embodiment, capacitor plates 15, 16 have a height of approximately 5 mm to approximately 20 mm, and preferably a height of approximately 10 mm. In addition, capacitor plates 15, 16 have a distance between them in the range of approximately 5 mm to approximately 30 mm. Most preferably the distance between capacitor plates 15,16 is at least 10% greater than the width of a tablet 4. In any case, reference models corresponding to the type of tablet in question should be recorded in advance so that sensor 12 can be calibrated for the area of application in question. In this way it is possible not only to count tablets 4 during the filling process but also to verify the quantitative features of tablets 4. Specifically, such inspection and monitoring may discover and sort out in-line both broken tablets, two tablets arriving at the same time due to a failed separation of tablets 4 on feed device 2 or, in the preferred case, tablets with the wrong color, even before they arrive in container 14.

By means of the system described here, it is possible to analyze more than approximately 1,000 tablets per minute, wherein the data of tablet 4 are recorded by sensor 12 within a time window of less than approximately 100 ms, preferably a time window of less than approximately 50 ms, and even more preferably a time window of less than approximately 10 ms.

The term “tablet” or “tablets” should be construed to cover any solid pharmaceutical product including but not limited to capsules, cap lets, gelatin, soft gel and the like.

While the invention is shown in several forms, it is not limited to those embodiments illustrated, but is susceptible to various changes and modifications without departing from the spirit and scope of the invention. 

1. A device for the monitored filling of containers with tablets, comprising a feed device for feeding tablets to a free-fall section, a capacitive sensor for checking each falling tablet in the free-fall section, a separating device for separating the bad tablets from the good tablets, the separating device being located below the sensor in the free-fall section, and a control unit, which is connected to the separating device and is adapted to actuate the separating device on the basis of the values supplied by the sensor.
 2. The device according to claim 1, wherein the sensor comprises a voltage generator for a high-frequency alternating electrical field, two opposing, vertically oriented capacitor plates given opposite, rapidly reversing charges by the voltage generator, and an ammeter.
 3. The device according to claim 2, wherein the alternating electrical field has a frequency in the range between approximately 500 kHz and approximately 10 MHz.
 4. The device according to claim 1, wherein the sensor is able to detect more than approximately 1,000 tablets per minute.
 5. The device according to claim 1, wherein the sensor is able to record the data of a tablet within a time window of less than approximately 100 ms.
 6. The device according to claim 2, wherein the capacitor plates have a height of approximately 5 to approximately 20 mm, and the distance between them is in the range of approximately 5 to approximately 30 mm.
 7. The device according to claim 1, further comprising a camera, which is positioned above the sensor and is connected to the control unit.
 8. The device according to claim 7, wherein the control unit is adapted to actuate the separating device on the basis of the information supplied by the camera.
 9. The device according to claim 1, wherein the separating device is designed as an air blast device, which aims a jet of air sideways against selected falling tablets.
 10. A method for the monitored filling of containers with tablets comprising the steps of: feeding tablets to a free-fall section; checking each falling tablet in the free-fall section by means of a capacitive sensor; separating, in a controlled manner, the bad tablets from the good tablets underneath the sensor in the free-fall section on the basis of the values supplied by the sensor.
 11. The method according to claim 10, wherein the sensor records the data of a tablet within a time window of less than approximately 100 ms.
 12. The method according to claim 10, wherein a camera above the sensor records information on each tablet, and this information is used together with the values supplied by the sensor as a basis for controlled separation.
 13. The method according to claim 10, wherein the separation step comprises the step of aiming a jet of air sideways against selected falling tablets. 